You start with a central idea. Usually, this will be the title of your story.

Example: This already exists, copyrighted by me and time/date-stamped on my hard-drive. I’m not worried about it being copied… as a central idea I’ll use the title of that novel:

Koan and Luger

Each separate and related idea is called a node. Each one is connected as a branch. Each idea related to a node connects to that node. The result is like a tree in which each branch is like a thinner one, as it gets further from the center.

Note that they can be done by hand with paper and pencil. The only drawback with that is the fact that unlike with a computer app you can’t collapse the lines that you’ve made. As a result you’ll have to use many pieces of paper. That’s a minor thing to most. I just try not to squander resources, so pixels on a screen are preferable to me.

Ideas often don’t come to mind in an order, so you may have many nodes all around a map. You may even have a separate map for different parts of your story. You may have a different map for your plot, one for your characters, etcetera — or you may keep them on the same map in separate nodes/branches. If so, that’s fine; the way you use them isn’t regulated.